Low dielectric constant materials are of increasing interest for providing a dielectric layer in semiconductor processing. Certain low dielectric materials, for example certain polymers or other organic materials, behave similarly to photoresist materials when etched. As a result, etching structures such as trenches and vias into these materials is difficult using conventional photolithographic techniques. For example, a large thickness of photoresist may be required to etch a trench or via. Such a thick layer of photoresist makes photolithography difficult, particularly when using shorter wavelength light to pattern the photoresist. In addition, when excess photoresist is removed, the underlying dielectric layer is attacked. Consequently, any structures etched into the dielectric will be affected by removal of the photoresist.
An etch hardmask is conventionally used to process such materials. The hardmask is etched at a much lower rate than the material contained in the underlying layer. The hardmask, therefore, allows the underlying layer to be processed without excessive thicknesses of photoresist. Typically, the etch hardmask is deposited using chemical vapor deposition ("CVD"). Once the hardmask is deposited and patterned, the underlying layer can be etched. Although CVD allows deposition of the hardmask, the CVD apparatus is relatively complex, expensive, and has throughput limitations. In addition, the CVD process requires relatively high temperatures, which may damage the underlying layer. Finally, the materials used to form a hardmask using CVD are subject to stresses which may lead to failures in the semiconductor device when the temperature is decreased.
Accordingly, what is needed is a system and method for easily, inexpensively, and rapidly providing an etch hardmask. The present invention addresses such a need.